Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $87.90   8.759%   $95.5992   $95.60   $95.60   $95.60  
  Purchase #2 $143.69   10.811%   $159.2243   $159.22   $159.20   $159.20  
  Purchase #3 $130.69   13.608%   $148.4743   $148.47   $148.45   $148.50  
  Purchase #4 $245.86   12.549%   $276.713   $276.71   $276.70   $276.70  
  Purchase #5 $30.77   10.533%   $34.011   $34.01   $34.00   $34.00  
  Purchase #6 $194.40   3.671%   $201.5364   $201.54   $201.55   $201.50  
  Purchase #7 $165.77   9.318%   $181.2164   $181.22   $181.20   $181.20  
  7 purchase totals = $999.08       $1,096.7746   $1,096.77   $1,096.70   $1,096.70